Fracture toughness test method

Abstract

An improved method for testing fracture toughness of tungsten carbide, and more particularly sintered tungsten carbide, consists of preparing a specimen from a short rod of sample material by cutting thin longitudinal slots forming a V within the slotted portion of the sample. An initial crack is started at the tip of the V formed by the slots. After the initial crack is started, the specimen is loaded with a force perpendicular to the slot plane and the peak force required in advancing the crack is recorded. The peak force is linearly related to the critical stress intensity factor (fracture toughness) of the specimen material.

I claim: 
     
       1. A method of preparing a test specimen for fracture toughness testing comprising selecting a short rod-shaped test specimen of a hard brittle material, and   cutting opposed longitudinal slots in said specimen in a single plane, intersecting said slots to form a single slot and stopping said opposed cutting a point short of the end of said specimen to form an internal V shape.   
     
     
       2. A method according to claim 1 in which said slots are cut in the center plane of said specimen. 
     
     
       3. A method according to claim 1 in which said hard brittle material comprises tungsten carbide.